Fe(III) Docking-Activated Sites in Layered Birnessite for Efficient Water Oxidation

Non-noble metal catalysts for promoting the sluggishkinetics ofoxygen evolution reaction (OER) are essential to efficient water splittingfor sustainable hydrogen production. Birnessite has a local atomicstructure similar to that of an oxygen-evolving complex in photosystemII, while the catalytic activity of birnessite is far from satisfactory.Herein, we report a novel Fe-Birnessite (Fe-Bir) catalyst obtainedby controlled Fe-(III) intercalation- and docking-induced layer reconstruction.The reconstruction dramatically lowers the OER overpotential to 240mV at 10 mA/cm(2) and the Tafel slope to 33 mV/dec, makingFe-Bir the best of all the reported Bir-based catalysts, even on parwith the best transition-metal-based OER catalysts. Experimental characterizationsand molecular dynamics simulations elucidate that the catalyst featuresactive Fe-(III)-O-Mn-(III) centers interfaced with orderedwater molecules between neighboring layers, which lower reorganizationenergy and accelerate electron transfer. DFT calculations and kineticmeasurements show non-concerted PCET steps conforming to a new OERmechanism, wherein the neighboring Fe-(III) and Mn-(III) synergisticallyco-adsorb OH* and O* intermediates with a substantially reduced O-Ocoupling activation energy. This work highlights the importance ofelaborately engineering the confined interlayer environment of birnessiteand more generally, layered materials, for efficient energy conversioncatalysis.

Automated summary

Non-noble metal catalyst Fe-Birnessite (Fe-Bir) was synthesized by controlled Fe-(III) intercalation- and docking-induced layer reconstruction, with significantly improved catalytic activity for the oxygen evolution reaction (OER). The Fe-Bir catalyst exhibited lower OER overpotential and Tafel slope compared to other Bir-based catalysts, and it featured active Fe-(III)-O-Mn-(III) centers interfaced with ordered water molecules between neighboring layers. This study reveals a new OER mechanism and highlights the importance of engineering the confined interlayer environment for efficient energy conversion catalysis.